Chunk parsing (WIP)

fmp/fmp_file.go

@@ -0,0 +1,142 @@
+package fmp
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"os"
+	"time"
+)
+
+const (
+	magicSequence = "\x00\x01\x00\x00\x00\x02\x00\x01\x00\x05\x00\x02\x00\x02\xC0"
+	hbamSequence  = "HBAM7"
+
+	magicSize        = len(magicSequence)
+	hbamSize         = len(hbamSequence)
+	sectorSize       = 4096
+	sectorHeaderSize = 20
+)
+
+type FmpFile struct {
+	VersionDate time.Time
+	CreatorName string
+	FileSize    uint
+	NumSectors  uint
+	Stream      io.ReadSeeker
+	Sectors     []*FmpSector
+}
+
+type FmpSector struct {
+	Deleted      bool
+	Level        uint8
+	PrevSectorID uint32
+	NextSectorID uint32
+	Chunks       []*FmpChunk
+}
+
+func OpenFile(path string) (*FmpFile, error) {
+	info, err := os.Stat(path)
+	if err != nil {
+		return nil, err
+	}
+
+	stream, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer stream.Close()
+
+	ctx := &FmpFile{Stream: stream}
+	if err := ctx.readHeader(); err != nil {
+		return nil, err
+	}
+
+	ctx.FileSize = uint(info.Size())
+	ctx.NumSectors = ctx.FileSize / sectorSize
+	ctx.Sectors = make([]*FmpSector, ctx.NumSectors)
+
+	for i := uint(0); i < ctx.NumSectors; i++ {
+		sector, err := ctx.readSector()
+		if err != nil {
+			return nil, err
+		}
+		ctx.Sectors[i] = sector
+	}
+
+	return ctx, nil
+}
+
+func (ctx *FmpFile) readHeader() error {
+	buf := make([]byte, sectorSize)
+	_, err := ctx.Stream.Read(buf)
+	if err != nil {
+		return err
+	}
+	if !bytes.Equal(buf[:magicSize], []byte(magicSequence)) {
+		return ErrBadMagic
+	}
+	if !bytes.Equal(buf[magicSize:magicSize+hbamSize], []byte(hbamSequence)) {
+		return ErrBadMagic
+	}
+
+	ctx.VersionDate, err = time.Parse("06JAN02", string(buf[531:538]))
+	if err != nil {
+		return ErrBadHeader
+	}
+
+	appNameLength := int(buf[541])
+	ctx.CreatorName = string(buf[542 : 542+appNameLength])
+
+	return nil
+}
+
+func (ctx *FmpFile) readSector() (*FmpSector, error) {
+	buf := make([]byte, sectorHeaderSize)
+	n, err := ctx.Stream.Read(buf)
+
+	if n == 0 {
+		return nil, io.EOF
+	}
+	if err != nil {
+		return nil, ErrRead
+	}
+
+	sector := &FmpSector{
+		Deleted:      buf[0] != 0,
+		Level:        uint8(buf[1]),
+		PrevSectorID: binary.BigEndian.Uint32(buf[2:6]),
+		NextSectorID: binary.BigEndian.Uint32(buf[6:10]),
+	}
+
+	payload := make([]byte, sectorSize-sectorHeaderSize)
+	n, err = ctx.Stream.Read(payload)
+	if n != sectorSize-sectorHeaderSize {
+		return nil, ErrRead
+	}
+	if err != nil {
+		return nil, ErrRead
+	}
+	sector.Chunks = make([]*FmpChunk, 0)
+
+	for {
+		chunk, err := ctx.readChunk(payload)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+		sector.Chunks = append(sector.Chunks, chunk)
+		if chunk == nil {
+			break
+		}
+		if chunk.Length == 0 {
+			panic("chunk length not set")
+		}
+		print(chunk.String() + "\n")
+		payload = payload[chunk.Length:]
+	}
+
+	return sector, nil
+}